Design Optimization on Centrifugal Compressor

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MECHANICAL ENGINEERING- CENTRIFUGAL COMPRESSOR
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DESIGN OPTIMIZATION ON CENTRIFUGAL COMPRESSOR
Introduction
A centrifugal compressor is one of its class machines in producing pressure rise and is known as
a turbo-compressors. In the centrifugal compressor, the energy is transferred by the dynamic
means from a rotating member (or impeller) to the continuously flowing working fluid
(Braembussche, 2019).
Centrifugal compressor is also referred to as radial compressor and it belongs to a sub-class of
dynamic axisymmetric work –absorbing turbomachinery. The centrifugal compressors
normally achieve pressure rise through the additional of kinetic velocity/ energy to a
continuous flow of fluid through the impeller or rotor. The kinetic energy is in most cases then
converted to increase in potential energy/ static pressure by slowing the flow through a diffuser.
The pressure rise in most cases almost equal to the rise in the diffuser.
Components of a simple centrifugal compressor
The main features of the centrifugal compressor is that the angular momentum of the fluid
which flows through the is partly increased by the virtue of the impeller’s outlet diameter
being larger as compared to the diameter of the inlet (Kim, Samad, & Benini, 2017). The
figure below is an illustration of the main components of a compressor.

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(American Society of Mechanical Engineers, 2015)
Essential components of a centrifugal compressor.
The centrifugal compressor is made up of the following parts:
i) The inlet
The casing of the inlet has a converging nozzle. The main function of this converging nozzle is
to assist in accelerating the fluid to the impeller inlet. The inlet casing has an outlet which is
referred to as an ‘eye’ (Esther Andrés-Pérez, Gauger, Quagliarella, & Giannakoglou,
2018)
ii) The impeller
The transfer of energy takes place in this component, with the transfer of energy, a rise in the
fluid static pressure and kinetic energy is achieved.
iii) The diffuse

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The main function of the diffuse is to convert the high kinetic energy of the fluid present in the
impeller outlet into static pressure.
iv) The outlet casing
The outlet casing is made up of a fluid collector which is also referred to as the scroll or volute.
The working principle of centrifugal compressor
The working principle of a centrifugal compressor is different from the reciprocating or rotary
compressors. When the air passes through the rotating impeller it experiences work or force
which is performed by the centrifugal forces (IMechE., 2014). Normally the work input occurs
when there is an increase in velocity and pressure of the air which flows through the impeller. As
the air flows it loses its velocity the moment it enters the diffuser section. The diffuser is
normally static or fixed element which escorts the air flow the moment it leaves the
impeller. The reduction in speed finally leads to an increase in pressure. The diffuser and the
impeller normally contributes to 35% and 65% of the total pressure which is produced or
developed in the compressor.
The performance of the centrifugal compressor is influenced by a number of factors thus
optimization of the centrifugal compressors can lead to superior design. Identifying the most
essential parameters influencing the performance of the centrifugal compressors greatly assists in
lowering the optimization process and cost of optimization (Amano & Sundén, 2010). The
impeller is the most important components of the centrifugal compressors as far as the design
optimization is concerned. It is very important to take into consideration all the factors which
effects its performance.